Pedicle Screw Insertion— Manual and Power Techniques



Pedicle Screw Insertion— Manual and Power Techniques


David B. Bumpass

Ronald A. Lehman Jr

Lawrence G. Lenke





PREOPERATIVE PREPARATION

On physical examination, standing coronal and sagittal spinal balance should be noted. Shoulder balance, rib prominence, truncal shift, and pelvic obliquity also must be assessed. Having the patient lie prone on the examination table is useful to determine scoliosis flexibility; a push-prone maneuver can also be done to further examine flexibility. For kyphotic patients, having the patient lie supine or prone is very useful to visualize how much passive correction can be achieved. A thorough neurologic exam to detect motor and sensory deficits as well as signs of myelopathy must be performed prior to deformity correction. The skin of the back should also be inspected for acne or previous incisions.

The patient’s preoperative radiographs should be reviewed in detail prior to beginning surgery. Pedicle morphology should be assessed on a full-length anterior-posterior (AP) spine radiograph— there is significant variability in pedicle diameter between patients, and the surgeon should have an excellent understanding of the vertebral morphology prior to starting the surgery. In scoliotic patients, pedicle diameter is affected by whether the pedicle is located on the concavity or convexity
of a curve. Studying the preoperative supine coronal radiograph is very helpful, as the pedicles are always more visible due to having less curvature, rotation, and movement when the radiograph is taken without gravity. In addition, the severity of vertebral rotation can be ascertained from the AP radiograph. The lateral radiograph is useful to estimate desired pedicle screw length.

For pediatric patients with complex deformities, such as severe scoliosis, previous fusions, or a congenital osseous abnormality, a preoperative thoracolumbar computed tomography (CT) scan is typically obtained. While recognizing the need to minimize radiation in children, CT imaging is extremely useful for studying pedicle diameter and morphology, plotting screw length, and creating three-dimensional reconstructions of the spine to fully understand the orientation of each segment of the deformity.

Magnetic resonance imaging is obtained in patients with significant kyphosis, a sharp angular or rapidly progressing scoliosis, an atypical curve pattern such as a left-sided scoliosis, or a known history of Chiari malformation or spinal dysraphism. Knowing whether a patient is at higher risk for neurologic deficit is a critical step in preoperative planning regarding implant selection and correction strategy.

Pedicle screws can be placed using a freehand technique based on posterior spinal anatomic landmarks; alternatively, screw placement can be guided using intraoperative fluoroscopy or CT-based navigation. One advantage of the freehand technique is minimization of radiation exposure. For surgeons who do not place a high volume of pedicle screws or are accumulating experience, using fluoroscopy or navigation might be helpful to minimize complications, as studies have noted a high learning curve for the freehand technique (3). Surgeons should use the technique they feel is safest and most efficacious for the patient. However, understanding the local osseous and neural anatomy necessary for placing screws without any image guidance will help all surgeons during whatever technique they choose. The remainder of this chapter will present the freehand technique.


Jun 13, 2016 | Posted by in ORTHOPEDIC | Comments Off on Pedicle Screw Insertion— Manual and Power Techniques

Full access? Get Clinical Tree

Get Clinical Tree app for offline access